Process and apparatus for the production of synthesis gas

ABSTRACT

A process for the production of synthesis gas from a hydrocarbon fuel and steam and/or oxygen gas wherein at least part of any steam requirement is provided by heat exchange against exhaust gas from a gas turbine driving an air separation unit supplying at least part of any oxygen requirement for the synthesis gas production. The process is particularly applicable when the synthesis gas is used to prepare a synfuel by methanol synthesis or a Fischer-Tropsch process.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a process and apparatus for theproduction of synthesis gas, particularly for but not necessarilylimited to, use in the production of hydrocarbon oils and waxes usingthe Fischer-Tropsch (“F-T”) process or methanol by catalytichydrogenation of carbon monoxide.

BACKGROUND OF THE INVENTION

[0002] Natural gas may be found in remote locations both on- andoffshore. It is is generally expensive and impractical to transportnatural gas from its source to a distant processing plant. One solutionis to convert the gas on-site to a valuable and easily transportableproduct. In this way, the value of the natural gas may be increased.

[0003] Natural gas may be converted to “synthesis gas” which is amixture of carbon monoxide and hydrogen. Synthesis gas may be convertedto a solid or liquid synthetic fuel or “synfuel”. The synfuel has lessvolume per unit mass (i.e. has a greater density) than the natural gas.Accordingly, it is more economical to transport synfuel than acorresponding amount of natural gas.

[0004] One disadvantage of the onsite processing of natural gas is thatthe space available for the processing apparatus is often limited. Forexample, in situations where the source of natural gas is offshore, agas rig or a sea vessel is used to support the apparatus for extractingthe natural gas. The processing apparatus required to convert naturalgas into synfuel must be as compact and as lightweight as possiblewithout sacrificing efficiency, productivity or cost-effectiveness. Afurther disadvantage is that the remote locations of the processingplants require that the plants are as self-sufficient as possible in theproduction of power to drive associated apparatus.

[0005] Examples of synfuels include high molecular weight hydrocarboncompounds produced using the F-T process and methanol produced by thecatalytic hydrogenation of carbon monoxide, Between 50 and 60% of thetotal cost of an F-T liquid or a methanol plant is in the production ofthe synthesis gas. Clearly, if the cost effectiveness of the synthesisgas generation process is adversely effected in attempting to overcomethese disadvantages, the overall processing costs of synfuel productioncould be significantly increased.

[0006] There are several methods of producing synthesis gas from naturalgas. Three such methods are based on the following processes:

[0007] Steam methane reforming (“SMR”) which needs imported carbondioxide or the consumption of excess hydrogen to achieve the required2:1 ratio for the relative proportions of hydrogen and carbon monoxidein the resultant synthesis gas.

[0008] Partial oxidation (“POX”) of natural gas with pure oxygen whichachieves a hydrogen to carbon monoxide ratio in the resultant synthesisgas of from 1.6 to 1.8:1.

[0009] Autothermal reforming (“ATR”) which consists of a partialoxidation burner followed by a catalyst bed with a feed of natural gas,steam and oxygen to produce the required 2:1 ratio for the relativeproportions of hydrogen and carbon monoxide in the resultant synthesisgas.

[0010] Each of these three processes produces high temperature synthesisgas (SMR 800 to 900° C., POX 1200 to 1400° C. and ATR 900 to 1100° C.).The excess heat generated in these processes may be used to generatesteam which, in turn, can be used in steam turbines to drive airseparation systems, air compressors and other equipment. The excess mayalso be used in part in a secondary gas heated catalytic reformer(“GHR”). For a POX/GHR combination, the synthesis gas is typicallyproduced at 500-600° C.

[0011] Carbon dioxide and methane are well known to have “greenhousegas” properties. It is, therefore, desirable that processes for theproduction of F-T liquids and methanol have low emission levels of thesegreenhouse gases and other pollutants, for example, oxides of nitrogen(“NO_(x)”).

[0012] It is, therefore, desirable that the processing of natural gas toproduce F-T liquids or methanol using synthesis gas is as efficient interms of yield and capital and running costs as possible with minimalemissions and power wastage. In addition, the plant should be compactand lightweight, particularly if located offshore.

[0013] Various attempts have been made to develop processes displayingat least some of these desiderata. Attempts to integrate certain stepsof the component processes are known to achieve some of these goals.Examples of such attempts are disclosed in WO-A-0003126 (Fjellhaug etal), WO-A-9832817 (Halmo et al) and WO-A-0009441 (Abbott).

[0014] U.S. Pat. No. 4,132,065 (McGann; published 2^(nd) January 1979)discloses a continuous partial oxidation gasification process forproducing synthesis gas. A hydrocarbonaceous fuel such as natural gas isreacted with a free oxygen containing gas, preferably air, optionally inthe presence of a temperature moderator such as steam or water toproduce synthesis gas. A portion of the synthesis gas is combusted inthe presence of compressed air to produce a combustion product gas whichis expanded in a gas turbine. Free oxygen containing gas is provided bya compressor that is driven by at least a portion of the power generatedby the expansion of the combustion product gas in the gas turbine.

[0015] It is the primary objective of this invention to improve theefficiency and lower the capital and operation costs of a synthesis gasgeneration process. A further objective of the invention is to reducegreenhouse gas emissions from such a process. The process is to haveparticular application in the production of synfuels.

SUMMARY OF THE INVENTION

[0016] It has been found that, by integrating a synthesis gas generationprocess with a gas turbine producing power, at least a portion of whichmay be used to drive a cryogenic air separation unit (“ASU”), processefficiency can be increased and process cost reduced. In addition,greenhouse gas emissions can be reduced and the plant can be made morecompact and lightweight. Further, there is an improvement in the levelof self-sufficiency in respect of power generation.

[0017] Hydrocarbon fuel gas is reacted with steam and/or oxygen gas in asynthesis gas generation system to produce a synthesis gas productstream. An oxidant gas is compressed to produce a compressed oxidantgas, at least a portion of which is combusted in the presence ofcombustion fuel gas to produce combustion product gas. The combustionproduct gas is expanded to produce power and expanded combustion productgas. Heat from the expanded combustion product gas is recovered by usingthe expanded combustion product gas to heat steam by heat exchange toproduce heated steam, at least a portion of which is used to provide atleast a portion of any steam requirement for producing the synthesis gasproduct stream in the synthesis gas generation system. Additionally oralternatively, at least a portion of the oxygen gas is provided using anASU that is driven by at least a portion of the power generated by theexpansion of the combustion product gas.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a flowsheet describing one embodiment of the process ofthe present invention in combination with an F-T process to producehydrocarbon oils and/or waxes.

DETAILED DESCRIPTION OF THE INVENTION

[0019] According to a first aspect of the present invention, there isprovided a process for the production of synthesis gas, said processcomprising:

[0020] reacting hydrocarbon fuel gas with steam and/or oxygen gas in asynthesis gas generation system to produce a synthesis gas productstream;

[0021] compressing an oxidant gas to produce a compressed oxidant gas;

[0022] combusting combustion fuel gas in the presence of at least aportion of said compressed oxidant gas to produce combustion productgas;

[0023] expanding said combustion product gas to produce power andexpanded combustion product gas;

[0024] heating a first steam stream by heat exchange against a stream ofsaid expanded combustion product gas to produce a heated first steamstream and using at least a portion of said heated first steam stream toprovide at least a portion of the steam for producing the synthesis gasproduct stream in the synthesis gas generation system; and/or

[0025] providing at least a portion of the oxygen gas using an ASU thatis driven by at least a portion of the power generated by the expansionof the combustion product gas.

[0026] Whilst the steps of compressing an oxidant gas, combustingcombustion fuel gas in the presence of compressed oxidant gas andexpanding the resultant combustion product gas can be carried out indedicated stand alone units, it is preferred that these steps arecarried out in a gas turbine system.

[0027] The synthesis gas generation system may comprise a POX, an ATR ora catalytic ATR. However, using these reactors alone may resultundesirably in a significant amount of waste heat. Therefore, inpreferred embodiments, the synthesis gas generation system comprises aGHR and the process comprises reforming hydrocarbon fuel gas with steamto produce synthesis gas.

[0028] The synthesis gas generation system may comprise a POX and GHR incombination. In these preferred embodiments, the process comprises:

[0029] partially oxidizing hydrocarbon fuel gas in the presence ofoxygen gas in the POX to produce a first intermediate synthesis gasstream; and

[0030] reforming hydrocarbon fuel gas with steam in the GHR to produce asecond intermediate synthesis gas stream and combining said intermediatesynthesis gas streams to produce the synthesis gas product stream.

[0031] In these embodiments, the POX/GHR system may generate synthesisgas using steam from a gas turbine waste heat recovery and steamgeneration system (“HRSG”). The steam from the HRSG provides for thedeficiency in heat input to the POX/GHR system. At least a portion ofthe power generated by the gas turbine is used, either directly orindirectly, to provide the power requirement of the ASU.

[0032] The oxidant gas may be selected from oxygen or air. In someembodiments, the oxidant gas is oxygen provided by an ASU although, inpreferred embodiments, the oxidant gas is air.

[0033] Preferably, the process further comprises:

[0034] heating water by heat exchange against the expanded combustionproduct gas stream to produce a heated second steam stream;

[0035] heating an oxygen gas stream by heat exchange against the heatedsecond steam stream to produce a heated oxygen gas stream; and

[0036] using said heated oxygen gas stream to provide at least a portionof the oxygen gas in the synthesis gas generation system.

[0037] The water to be heated to provide the heated second steam streammay be a liquid water stream, a two-phase (liquid-vapor) stream or asteam stream. In preferred processes, the heated second steam stream isa portion of the heated first steam stream.

[0038] The HRSG may produce excess steam. Introduction of this excesssteam into the combustion of the combustion fuel gas conditions the fuelgas which has the effect of increasing the power output of the gasturbine. The process may, therefore, further comprise:

[0039] heating water by heat exchange against the expanded combustionproduct gas stream to produce a heated third steam stream; and

[0040] introducing the heated third steam stream into the combustion ofthe combustion fuel gas.

[0041] The water to be heated to provide the heated third steam streammay be a liquid water stream, a two-phase (liquid-vapor) stream or asteam stream. In preferred embodiments, the heated third steam stream isan excess portion of the heated first steam stream. The introduction ofthe excess steam in this way further integrates the overall process.

[0042] An efficient process is one that is balanced, that is to say, aprocess in which there is no heat or material loss. In the presentinvention, the excess portion of the heated first steam stream issurprisingly low, i.e. about 3-wt %. The low level of excess steam wasunexpected and indicates that the process is substantially balanced.This is a significant advantage over the known processes.

[0043] In preferred embodiments, the hydrocarbon fuel gas comprisesmethane, natural gas, gas associated with oil production or combustibleoff-gases from downstream processes and the combustion fuel gascomprises hydrogen, methane, natural gas, gas associated with oilproduction or combustible off-gases from downstream processes. The useof natural gas as the hydrocarbon fuel gas and the combustion fuel gasis particularly preferred. The natural gas should be desulphurized if itis to come in contact with a solid catalyst.

[0044] In preferred embodiments, the combustion fuel gas comprisessubstantially pure hydrogen produced from the synthesis gas productstream. The use of hydrogen gas as the sole combustion fuel gas in thisway virtually eliminates all carbon dioxide emissions from the process.This is a further significant advantage of the present invention overthe prior art.

[0045] NO_(x) may be produced during the combustion of the combustionfuel gas. If released into the atmosphere, NO_(x) would act as apollutant. The level of NO_(x) emissions is reduced as the proportion ofnitrogen present in the combustion is increased. In addition, thecombustion fuel gas may be conditioned by introducing compressednitrogen into the combustion. This has the effect of increasing thepower output of the gas turbine due to the increase in mass of theexhaust gases. Therefore, the process may further comprise:

[0046] heating a compressed nitrogen stream by heat exchange against theexpanded combustion product gas stream to provide a heated compressednitrogen stream; and

[0047] introducing said heated compressed nitrogen stream into thecombustion of the combustion fuel gas.

[0048] Preferably, the compressed nitrogen stream is produced bycompressing a stream of nitrogen produced in an ASU. This step furtherintegrates the overall process.

[0049] In preferred embodiments, the expansion of the combustion productgas will produce more power than required to drive the ASU. Instead ofallowing a remaining portion of the power generated to be wasted, atleast a part of the remaining portion of the power generated may be usedto provide auxiliary power for downstream processes.

[0050] Once the synthesis gas product stream has been produced, it maybe used in a number of ways. In preferred embodiments of the presentprocess, the synthesis gas product stream or a stream derived therefromis processed in a synfuel generation system to produce a synfuel.

[0051] Preferably, the synfuel generation system comprises an F-Treactor and the synfuel is a mixture of high molecular weighthydrocarbon compounds.

[0052] The F-T reaction is a catalyzed reaction between carbon monoxideand hydrogen to produce a mixture of high and low molecular weighthydrocarbon compounds, carbon dioxide and water. The expression “highmolecular weight hydrocarbon compounds” includes hydrocarbon compoundshaving at least 6 carbon atoms that are readily condensable to form oilsor waxes. The expression “low molecular weight hydrocarbon compounds”includes gaseous C₁-C₅ hydrocarbon compounds that are not so readilycondensable as the high molecular weight hydrocarbon compounds. At leastportion of combustible off-gases generated in the F-T reactorcomprising, for example, these low molecular weight hydrocarbons may beintroduced as fuel into the combustion of the combustion fuel gas.Alternatively, a stream of at least a portion of the combustibleoff-gases generated in the F-T reactor or a stream derived therefrom maybe combined with hydrocarbon fuel gas to produce a combined gas stream.The combined gas stream or a stream derived therefrom may be fed as fuelto the synthesis gas generation system.

[0053] The F-T reaction is highly exothermic and may be expressed by thefollowing reaction scheme:

CO+H₂→—CH₂—+H₂O ΔH=−36.1 kcal/mol@25° C.

[0054] The overall efficiency of the process is improved by preheatingthe feed streams to the gas turbine and the synthesis gas generationsystem by heat exchange against either the expanded combustion productgas stream or the synthesis gas product stream in the usual way.

[0055] Methanol may be produced by the catalytic exothermichydrogenation of carbon monoxide according to the following reactionscheme:

CO+2H₂→CH₃OH ΔH=−49.43 kcal/mol@25° C.

[0056] To produce methanol, the synfuel generation system may comprise areactor provided with a carbon monoxide hydrogenation catalyst. Thesynthesis gas product stream (or a stream derived therefrom) may,therefore, be reacted in a reactor provided with a hydrogenationcatalyst to produce heat and a methanol product stream. Hydrogen,nitrogen and argon may be vented from the reactor.

[0057] The methanol product stream may comprise unreacted synthesis gasin which case the process may further comprise recycling the methanolproduct stream around the reactor until substantially all of theunreacted synthesis gas has been reacted.

[0058] In order to reduce emissions, originating from the methanolgeneration reactor, into the atmosphere, the process may furthercomprise:

[0059] removing a purge gas stream comprising unreacted synthesis andinert gas from the reactor; and

[0060] introducing at least a portion of said purge gas stream or astream derived therefrom as fuel into the combustion of the combustionfuel gas.

[0061] At least a portion of the purge gas stream may be recycled byfeeding to the synthesis gas generation system.

[0062] In any one of the methanol production processes, heat may beremoved from the methanol generation reactor by heat exchange withwater, preferably to form medium pressure steam.

[0063] According to a second aspect of the present invention, there isprovided apparatus for the production of synthesis gas according to theprocess of the first aspect of the present invention, said apparatuscomprising:

[0064] a synthesis gas generation system for reacting hydrocarbon fuelgas with steam and/or oxygen gas to produce a synthesis gas productstream;

[0065] compressing means for compressing an oxidant gas to producecompressed oxidant gas;

[0066] combusting means for combusting combustion fuel gas in thepresence of at least a portion of said compressed oxidant gas to producecombustion product gas;

[0067] expanding means for expanding said combustion product gas toproduce power and expanded combustion product gas;

[0068] heat exchange means for heating a first steam stream against astream of expanded combustion product gas to produce a heated firststeam stream;

[0069] conduit means for supplying the stream of expanded combustionproduct gas from the expanding means to the first heat exchange means;

[0070] conduit means for supplying at least a portion of the heatedfirst steam stream from the first heat exchange means to the synthesisgas generation system; and/or

[0071] an ASU;

[0072] means for transferring at least a portion of the power producedby the expanding means to the ASU; and

[0073] conduit means for supplying at least a portion of the oxygen gasfrom the ASU to the synthesis gas generation system.

[0074] Preferably, the apparatus is adapted to carry out any combinationof the optional features of the process described above. In particularlypreferred embodiments, the compressing means, the combusting means andthe expanding means are stages of a gas turbine.

EXAMPLE

[0075] The detailed configuration of the process depicted in FIG. 1depends on the downstream gas to liquids process and, in particular, theratio of hydrogen to carbon monoxide, the amount of carbon dioxide thatcan be tolerated and the amount and composition of the by-productsgenerated.

[0076] Referring to the FIG. 1, a natural gas stream 1, pressurized toabout 34 atm. (3.4 MPa), is divided into a first portion 2 and a secondportion 3. The first portion 2 is heated to about 300° C. by heatexchange against a hydrogen-enriched synthesis gas product stream 11 ina first heat exchanger X3 and is then fed to the POX R1 where it isreacted with oxygen. The second portion 3 is combined with a compresseduncondensed by-product stream 24 and fed to the GHR.

[0077] A stream 28 of oxygen is heated to about 270° C. in a second heatexchanger X1 against a stream of steam 39, pressurized to about 34 atm.(3.4 MPa) to produce a heated oxygen stream 29 and a cooled steam stream40. The heated oxygen stream 29 is fed to the POX R1 and reacted withnatural gas to produce a first intermediate synthesis gas. A stream 5 ofthe first intermediate synthesis gas leaves the POX at about 1305° C.and enters the shell-side of the GHR R2 where it is mixed with reformedgas exiting the open-ended reformer tubes. The gaseous mixture flows upthe side of the tubes, providing heat for the reforming being carriedout in the tubes, and exits the GHR as a synthesis gas product stream 6.

[0078] The synthesis gas product stream 6 leaves the GHR at about 500°C. and is cooled in a third heat exchanger X2 against, inter alia, aportion 33 of the steam, pressurized to about 35 atm. (3.5 MPa),required to produce the desired steam to carbon ratio of about 4:1 inthe GHR. This step produces a cooled synthesis gas product stream 7.

[0079] The ratio of hydrogen to carbon monoxide in the synthesis gasproduct stream 6 is about 1.65:1. However, this ratio may not beappropriate for certain downstream processes. For the present embodimentwhere the synthesis gas generated is to be used in an F-T process, ahigher ratio of between 1.9 to 2.3:1 is required. In this embodiment,the cooled synthesis gas product stream 7 is divided into a firstportion 8 and a second portion 9. The second portion 9 is fed to a hightemperature shift reactor (“HTS”) R3 to shift some of the carbonmonoxide to hydrogen. The resultant intermediate hydrogen-enrichedsynthesis gas stream 10 is combined with the first portion 8 thatbypassed the HTS to produce the hydrogen-enriched synthesis gas stream11 with the required ratio of hydrogen and carbon monoxide.

[0080] The hydrogen-enriched synthesis gas stream 11 is then cooled inthe first heat exchanger X3 against the vaporisation of a water stream30, pressurized to 35 atm. (3.5 MPa) and the heating of the natural gasstream 3. This exchange of heat produces the heated natural gas stream 4and a first steam stream 34 and a cooled hydrogen-enriched synthesis gasproduct stream 12.

[0081] The first steam stream 34 is further heated to about 430° C. in afourth heat exchanger X7 located in the HRSG to produce a heated firststeam stream 35. A first portion 36 of this stream is combined with thegas to be reformed in the GHR and a part 39 of a second portion 37 ofthis stream is used to pre-heat the oxygen stream 28 in the second heatexchanger X1. An excess part 38, amounting to approximately 3% by weightof the heated first steam stream 35, may be added to a combustor R5.

[0082] The cooled hydrogen-enriched synthesis gas product stream 12 isfurther cooled in a first condenser X4, thereby condensing steamcontaminants in the synthesis gas and producing a wet synthesis gasstream 13. Water is separated from the synthesis gas stream in aseparator vessel C1 to produce a first water by-product stream 51 and awater-depleted synthesis gas stream 14. The water-depleted synthesis gasstream 14 is then heated to a reaction temperature of about 240° C. inheat exchanger X5 and is fed as stream 15 to the F-T reactor R4 toproduce a first hydrocarbon product stream 16.

[0083] A very simplified F-T reactor is shown in the flowsheet. Theactual unit would be far more complex with more than one reactor,unreacted feed recycle and downstream processing to produce thedifferent cuts of fuel required. For this embodiment of the invention,the first hydrocarbon product stream produced contains about 64% byweight carbon dioxide. This is based on an F-T reactor system whichoperates at 28 atm. (2.8 MPa) and converts about 92% of the inlet carbonmonoxide to hydrocarbon compounds using a cobalt-based catalyst.

[0084] High molecular weight hydrocarbon compounds and steamcontaminants in first hydrocarbon product stream 16 are condensed in athird condenser X6. The condensed components in stream 17 are removedfrom the gaseous by-products in a second separator C2 to produce a wetcondensed hydrocarbon product stream 18 and an uncondensed by-productstream 21. The water is removed from the wet condensed hydrocarbonproduct stream 18 in a third separator C3 to produce a second waterby-product stream 20 and a second hydrocarbon product stream 19containing the high molecular weight hydrocarbon products.

[0085] A portion 22 of the uncondensed by-product stream 21 is vented toprevent the build up of inert gases such as nitrogen and argon. Thisportion can be added to the combustion fuel gas for the gas turbinecombustor R5. The remaining portion 23 is compressed in a compressor K3to about 32 atm. (3.2 MPa) and combined with natural gas 2 and thecombined stream 25 is heated to about 430° C. in the third heatexchanger X2 to produce a heated steam stream 26 that is combined withsteam to produce the GHR feed stream 27.

[0086] The remaining part of the flowsheet concerns the gas turbine andthe HRSG. A feed air stream 45 is compressed in a second compressor K1to about 12 atm. (1.2 MPa) and is then fed to the combustor R5 where itis used to combust natural gas. A stream 47 of combustion product gas isexpanded in an expander K2 to produce an expanded combustion product gasstream 48. The waste heat in the expanded gas stream 48 is recovered inthe HRSG against feed streams to the combustor and the POX/GHR system.

[0087] A natural gas stream 41 is heated in the HRSG to produce a heatednatural gas stream 42 that is fed to the combustor R5. A nitrogen stream43 is heated in the HRSG and the resultant heated nitrogen stream 44used to condition the heated natural gas stream 42 in the combustor R5.A second feed water stream 32 is heated in the HRSG to produce theheated water stream 33 that is fed to the third heat exchanger X2 whereit is vaporized to produce a second steam stream that is added to theGHR as feed stream 27.

[0088] The power generated by the gas turbine under iso-conditions is 93MW which is enough to provide the power for the ASU (57 MW) and a largepart of the power required for the downstream processes.

[0089] The heat and material balance for the exemplified process isprovided in the following Table 1: TABLE 1 Heat and Material Balance forFT production example under iso-conditions Mole Fraction 1 2 3 4 5 6 7 89 10 11 12 13 Oxygen 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Methane 86.08% 86.08% 86.08% 86.08% 0.24%0.39% 0.39% 0.39% 0.39% 0.39% 0.39% 0.39% 0.39% Carbon monoxide 0.00%0.00% 0.00% 0.00% 33.83% 23.45% 23.45% 23.45% 23.45% 11.48% 19.47%19.47% 19.47% Hydrogen 0.00% 0.00% 0.00% 0.00% 57.15% 37.70% 37.07%37.07% 37.07% 49.69% 41.67 41.67% 41.67% Carbon Dioxide 1.61% 1.61%1.61% 1.61% 1.38% 11.96% 11.96% 11.96% 11.96% 23.94% 15.93% 15.93%15.93% Water 0.00% 0.00% 0.00% 0.00% 7.13% 25.25% 25.25% 25.25% 25.25%13.26% 21.28% 21.28% 21.28% Argon 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% FT Liquid 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Ethane 8.02%8.02% 8.02% 8.02% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Propane 2.66% 2.66% 2.66% 2.66% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% Butane 0.57% 0.57% 0.57% 0.57% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Pentane 0.09% 0.09% 0.09% 0.09% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Isobutane 0.29% 0.29%0.29% 020% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%2-Methyl-Butane 0.10% 0.10% 0.10% 0.10% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% Hexane 0.05% 0.05% 0.05% 0.05% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Heptane 0.01% 0.01% 0.01% 0.01%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Nitrogen 0.52%0.52% 0.52% 0.52% 0.27% 1.20% 1.28% 1.28% 1.26% 1.26% 1.26% 1.26% 126%Total Flow KMOL/H 8585 1200 7385 7385 24282 54943 54943 38729 1821418214 54843 54843 54843 Temperature ° C. 25 25 25 300 1305 500 313 313313 443 357 174 40 Pressure BAR 34 34 34 34 34 32 32 32 32 32 32 32 32Pressure MPa 34 34 34 34 34 32 32 32 32 32 32 32 32 Vapor Fraction 1 1 11 1 1 1 1 1 1 1 1 0.79 Enthalpy J/KMOL −8.27+07 −8.27E+07 −8.27E+07−8.90E+07 −1.94E+07 −1.19E+08 −1.25E+08 −1.25E+08 −1.25E+08 −1.25E+08−1.25E+08 −1.31E+08 −1.45E+08 Average MW 18.94 18.94 18.94 18.94 12.6317.55 17.55 17.55 17.55 17.55 17.55 17.55 17.55 Mole Fraction 14 15 1617 18 19 20 21 22 23 24 25 26 Oxygen 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Methane 0.49% 0.49% 2.93%2.93% 0.00% 0.80% 0.00% 5.13% 5.13% 5.13% 5.13% 12.38% 12.38% Carbonmonoxide 24.68% 24.68% 3.58% 3.58% 0.02% 0.31% 0.00% 8.30% 8.30% 8.30%8.30% 5.73% 5.73% Hydrogen 52.83% 52.83% 10.07% 10.07% 0.03% 0.41% 0.01%17.78% 17.78% 17.78% 17.78% 16.17% 16.17% Carbon Dioxide 20.13% 20.13%37.02% 37.02% 1.31% 13.18% 0.49% 84.34% 84.34% 84.34% 64.34% 58.72%58.72% Water 0.27% 0.27% 40.02% 40.52% 93.05% 0.23% 99.50% 0.33% 0.33%0.33% 0.33% 0.30% 0.30% Argon 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% FT Liquid 0.00% 0.00% 2.25% 2.25%5.18% 76.79% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Ethane 0.00%0.00% 0.18% 0.18% 0.01% 0.22% 0.00% 0.32% 0.33% 0.32% 0.32% 1.01% 1.01%Propane 0.00% 0.00% 0.19% 0.19% 0.04% 0.59% 0.00% 0.30% 0.30% 0.30%0.30% 0.51% 0.51% Butane 0.00% 0.00% 0.18% 0.18% 0.09% 1.43% 0.00% 0.25%0.25% 0.25% 0.25% 0.28% 0.28% Pentane 0.00% 0.00% 0.18% 0.18% 0.18%2.84% 0.00% 0.16% 0.18% 0.18% 0.16% 0.18% 0.18% Isobutane 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.03% 0.03%2-Methyl-Butane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.01% 0.01% Hexane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Heptane 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Nitrogen 1.60%1.60% 2.80% 2.89% 0.03% 0.23% 0.00% 5.08% 5.08% 0.00% 5.00% 4.86% TotalFlow KMOL/H 43337 43337 23931 23921 10388 874 9694 13553 1355 1219812198 13398 13398 Temperature ° C. 40 240 250 40 40 43 42 40 40 40 52 46430 Pressure BAR 32 32 28 26 28 28 28 28 28 28 32 32 32 Pressure MPa 1 12.8 2.8 2.6 2.8 2.8 2.8 2.8 2.8 3.2 3.2 3.2 Vapor Fraction 1 0.57 0 0 01 1 1 1 1 1 Enthalpy J/KMOL −1.07E+08 −1.01E+08 −2.49E+08 −2.78E+08−2.94E+08 −1.19E+08 −2.85E+08 −2.86E+08 −2.86E+08 −2.88E+08 −2.85E+08−2.49E+08 −2.39E+08 Average MW 17.41 17.41 31.54 31.54 29.31 190.0118.14 33.25 33.24 22.35 22.35 31.97 31.97 Mole Fraction 27 28 29 30 3132 33 34 35 36 37 38 39 Oxygen 0.00% 99.50% 99.50% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Methane 8.35% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Carbonmonoxide 2.94% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% Hydrogen 8.29% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Carbon Dioxide 30.10% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Water 48.90%0.00% 0.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00%100.00% 100.00% 100.00% Argon 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% FT Liquid 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Ethane 0.52% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Propane 0.28% 0.00% 0.00% 0.00% 0 00% 0.00% 0.00% 0 00% 0.00% 0.00%0.00% 0.00% 0.00% Butane 0.14% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Pentane 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Isobutane 0.01% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%2-Methyl-Butane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% Hexane 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Heptane 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Nitrogen 2.40%0.50% 0.50% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Total Flow KMOL/H 26138 5212 5212 4545 2572 9432 2572 4545 11405 33091236 304 932 Temperature ° C. 428 25 270 25 0 25 100 340 430 430 430 430430 Pressure BAR 32 34 34 35 35 35 35 35 35 35 35 35 35 Pressure MPa 3.23.4 3.4 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 Vapor Fraction 1 1 1 0 10 0 1 1 1 1 1 1 Enthalpy J/KMOL −2.31E+08 −2.99E+08 7.38E+08 −2.86E+08−2.29E+08 −2.86E+08 −2.80E+08 −2.32E+08 −2.29E+08 −2.29E+08 −2.29E+08−2.29E+08 −2.29E+08 Average MW 25 31.98 31.98 18.02 18.02 18.02 18.0218.02 18.02 18.02 18.02 18.02 18.02 Mole Fraction 40 41 42 43 44 45 4647 48 49 50 51 52 Oxygen 0.00% 0.00% 0.00% 1.00% 1.00% 21.50% 21.50%11.94% 12.77% 12.77% 0.00% 21.50% 0.00% Methane 0.00% 86.08% 86.08%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Carbonmonoxide 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.01% 0.00% 0.01% Hydrogen 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.02% 0.00% 0.02% Carbon Dioxide 0.00% 1.61% 1.61%0.00% 0.00% 0.00% 0.00% 3.41% 3.11% 3.11% 0.26% 0.00% 0.26% Water100.00% 0.00% 0.00% 0.00% 0.00% 1.50% 1.50% 7.50% 6.98% 6.98% 99.70%1.50% 99.70% Argon 0.00% 0.00% 0.00% 0.00% 0.00% 1.00% 1.00% 0.85% 0.86%0.86% 0.00% 1.00% 0.00% FT Liquid 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Ethane 0.00% 8.02% 8.02% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Propane 0.00%2.66% 2.66% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Butane 0.00% 0.57% 0.57% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% Pentane 0.00% 0.09% 0.09% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Isobutane 0.00% 0.29% 0.29% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 2-Methyl-Butane 0.00%0.10% 0.10% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%Hexane 0.00% 0.05% 0.05% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% Heptane 0.00% 0.01% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00%0.00% 0.00% 0.00% 0.00% 0.00% Nitrogen 0.00% 0.52% 0.52% 99.00% 99.00%76.00% 78.00% 76.30% 76.28% 76.28% 0.00% 76.00% 0.00% Total Flow KMOL/H932 943 943 3784 3784 30465 27419 32225 35272 35272 11606 3047 11606Temperature ° C. 210.45 25 450 25 450 25 360 1133 549 100 40 380 40Pressure BAR 35 22.4 22.4 22.4 22.4 1.01 1195 1147 105 105 32 12 32Pressure MPa 3.5 2.24 2.24 2.2 2.2 0.1 1.2 1.1 0.1 0.1 3.2 1.2 3.2 VaporFraction 0 1 1 1 1 1 1 1 1 1 0 0 0 Enthalpy J/KMOL −2.72E+08 −8.24E+07−5.96E+07 −1.56E+08 1.27E+07 −3.64E+08 6.35E+06 5.13E+06 −1.29E+07−2.69E+07 −2.85E+08 6.35E+06 −2.85E+08 Average MW 18.02 18.94 18.9428.05 28.05 28.84 28.84 28.39 28.43 28.43 18.08 28.84 18.08

[0090] The exemplified embodiment of the present invention is comparedwith the Natural Gas Fischer-Tropsch Technology report carried out byBechtel Ltd for the U.S DOE Pittsburgh Energy Technology Center(Reference—U.S. Department of Energy Pittsburgh Energy TechnologyCenter—Baseline Design/Economics for advanced Fischer Tropsch TechnologyContract No. DE-AC22-91PC90027. Tropical Report VI—Natural Gas FischerTropsch Case Volume II Plant Design and Aspen Process SimulationModel—by Bechtel Ltd August 1996.) Basis Invention Saving Synthesis gaskmol/h 59860 59860 production Natural gas used MMSCFD 411.9 396  4%(Nm³/h) (4.51 × 10⁵) (4.33 × 10⁵) O₂ used (99.5% purity) MTD 11391 679140% (Kg/h) (4.75 × 10⁵) (2.83 × 10⁵) FT Gasoline produced Bbl/day 1703017030 (m³/h) (112.8) (112.8) FT Diesel produced Bbl/day 26210 26210(m³/h) (173.6) (173.6) Propane produced Bbl/day 1700 1700 (m³/h) (11.3)(11.3) Thermal Efficiency % 56.94% 58.57% (LHV - Lower Heating Value)

[0091] The invention FIGURES are based on non-iso conditions for the gasturbine performance. The Fischer Tropsch synthesis has been scaled fromthe basis case to give consistent results. The same natural gascomposition was also used to ensure the energy balances were alsoconsistent. Further, the computer simulation of the invention processincorporates a carbon dioxide recycle to the GHR (in order to make morehydrogen to balance the process) solely for comparative purposes. Thisrecycle step actually reduces the efficiency of the present invention.

[0092] In another embodiment of the present invention, a synthesis gasstream with a hydrogen to carbon monoxide ratio of about 2:1 and acarbon dioxide composition of about 5% is required for an F-T plant. TheF-T synthesis produces pure carbon dioxide and fuel gas as a by-product.For this flowsheet, the carbon dioxide is fed to the GHR as part of thefeed to achieve the required 2:1 hydrogen to carbon monoxide ratio inthe synthesis gas stream. The fuel gas has a high enough calorific valueto be used instead of natural gas in the gas turbine. The steam tocarbon ratio required is about 2.2:1 for this case so the excess steamproduced in the HRSG is added to the fuel for the gas turbine. Thisconditions the fuel in the gas turbine and will help to reduce theNO_(x) emissions from turbine. The other significant change is thatthere is no longer any need to shift carbon monoxide to hydrogen so theshift reactor is omitted from the flowsheet.

[0093] It will be appreciated that the invention is not restricted tothe details described above with reference to the preferred embodimentsbut that numerous modifications and variations can be made withoutdeparting from the scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A process for the production of synthesis gas,said process comprising: reacting hydrocarbon fuel gas with steam and/oroxygen gas in a synthesis gas generation system to produce a synthesisgas product stream; compressing an oxidant gas to produce a compressedoxidant gas; combusting combustion fuel gas in the presence of at leasta portion of said compressed oxidant gas to produce combustion productgas; expanding said combustion product gas to produce power and expandedcombustion product gas; heating a first steam stream by heat exchangeagainst a stream of said expanded combustion product gas to produce aheated first steam stream and using at least a portion of said heatedfirst steam stream to provide at least a portion of the steam forproducing the synthesis gas product stream in the synthesis gasgeneration system; and/or providing at least a portion of the oxygen gasusing an air separation unit (“ASU”) that is driven by at least aportion of the power generated by the expansion of the combustionproduct gas.
 2. The process according to claim 1 wherein the synthesisgas generation system comprises a gas heated reformer (“GHR”), saidprocess further comprising reforming hydrocarbon fuel gas with steam toproduce synthesis gas.
 3. The process according to claim 1 wherein thesynthesis gas generation system comprises a partial oxidation reactor(“POX”) and a GHR in combination, said process further comprising:partially oxidizing hydrocarbon fuel gas in the presence of oxygen gasin the POX to produce a first intermediate synthesis gas product; andreforming hydrocarbon fuel gas with steam in the GHR to produce a secondintermediate synthesis gas product and combining said intermediatesynthesis gas products to produce the synthesis gas product stream. 4.The process according to claim 1 wherein the synthesis gas generationsystem comprises an autothermal reformer (“ATR”).
 5. The processaccording to claim 1 further comprising: heating water by heat exchangeagainst the expanded combustion product gas stream to produce a heatedsecond steam stream; heating an oxygen gas stream by heat exchangeagainst the heated second steam stream to produce a heated oxygen gasstream; and using said heated oxygen gas stream to provide at least aportion of the oxygen gas in the synthesis gas generation system.
 6. Theprocess according to claim 5 wherein the heated second steam stream is aportion of the heated first steam stream.
 7. The process according toclaim 1 further comprising: heating water by heat exchange against theexpanded combustion product gas stream to produce a heated third steamstream; and introducing the heated third steam stream into thecombustion of the combustion fuel gas.
 8. The process according to claim7 wherein the heated third steam stream is an excess portion of theheated first steam stream.
 9. The process according to claim 1 whereinthe hydrocarbon fuel gas is selected from the group consisting ofmethane, natural gas, gas associated with oil production and combustibleoff-gases from downstream processes and the combustion fuel gas isselected from the group consisting of hydrogen, methane, natural gas,gas associated with oil production and combustible off-gases fromdownstream processes.
 10. The process according to claim 1 wherein thecombustion fuel gas comprises substantially pure hydrogen produced fromthe synthesis gas product stream.
 11. The process according to claim 1further comprising: heating a compressed nitrogen stream by heatexchange against the expanded combustion product gas stream to provide aheated compressed nitrogen stream; and introducing said heatedcompressed nitrogen stream into the combustion of the combustion fuelgas.
 12. The process according to claim 11 further comprising producingsaid compressed nitrogen stream by compressing a stream of nitrogenproduced in an ASU.
 13. The process according to claim 1 furthercomprising processing the synthesis gas product stream or a streamderived therefrom in a synfuel generation system to produce a synfuel.14. The process according to claim 13 wherein the synfuel generationsystem comprises a Fischer-Tropsch (“F-T”) reactor and the synfuel is amixture of high molecular weight hydrocarbon compounds.
 15. The processaccording to claim 14 wherein combustible off-gases are generated in theF-T reactor and at least a portion of said combustible off-gases areintroduced into the combustion of the combustion fuel gas.
 16. Theprocess according to claim 14 wherein combustible off-gases aregenerated in the F-T reactor and a stream of at least a portion of saidcombustible off-gases or a stream derived therefrom is combined withhydrocarbon fuel gas to produce a combined gas stream, said combined gasstream or a stream derived therefrom being fed as fuel to the synthesisgas generation system.
 17. The process according to claim 13 wherein thesynfuel generation system comprises a reactor provided with a carbonmonoxide hydrogenation catalyst and the synfuel is methanol.
 18. Theprocess according to claim 17 further comprising: removing a purge gasstream comprising unreacted synthesis gas and inert gas from thereactor; and introducing at least a portion of the purge gas stream or astream derived therefrom as fuel into the combustion of the combustionfuel gas.
 19. The process according to claim 17 further comprising:removing a purge gas stream from the reactor; combining the purge gasstream or a stream derived therefrom with hydrocarbon fuel gas toproduce a combined purge gas stream; and feeding at least a portion ofthe combined purge gas stream to the synthesis gas generation system.20. Apparatus for the production of synthesis gas according to theprocess of claim 1, said apparatus comprising: a synthesis gasgeneration system for reacting hydrocarbon fuel gas with steam and/oroxygen gas to produce a synthesis gas product stream; compressing meansfor compressing an oxidant gas to produce compressed oxidant gas;combusting means for combusting combustion fuel gas in the presence ofat least a portion of said compressed oxidant gas to produce combustionproduct gas; expanding means for expanding said combustion product gasto produce power and expanded combustion product gas; heat exchangemeans for heating a first steam stream against a stream of expandedcombustion product gas to produce a heated first steam stream; conduitmeans for supplying the stream of expanded combustion product gas fromthe expanding means to the first heat exchange means; conduit means forsupplying at least a portion of the heated first steam stream from thefirst heat exchange means to the synthesis gas generation system; and/oran ASU; means for transferring at least a portion of the power producedby the expanding means to the ASU; and conduit means for supplying atleast a portion of the oxygen gas from the ASU to the synthesis gasgeneration system.